Developing a Joomla Extension

i’m building a Joomla based website with a lot of content categories.
most of the content will be created manually in Joomla’s admin panel (or through the frontend), but the content items in some categories (of the content component) need to be created automatically based on data that exist in an external database.

additionally, i need to create site users based on existing users in an external system.

please see the attached file for a full mockup of the extension.